re: How much to file for a patent?

I'm a patent lawyer. All in costs on a simple patent range from 10-20k. It's generally true that you get what you pay for.

I tell everyone with an idea they want to patent that getting the patent is the easy part. Starting a business around it is much more difficult.

Also, if you want to be cynical about it, a patent is just a lottery ticket to litigation. That's not exactly true, but it's not exactly false either.